Freezing an Android phone can help reveal its confidential contents, German security researchers have found.

The team froze phones for an hour as a way to get around the encryption system that protects the data on a phone by scrambling it.

Google introduced the data scrambling system with the version of Android known as Ice Cream Sandwich.

The attack allowed the researchers to get at contact lists, browsing histories and photos.

Cold start

Android's data scrambling system was good for end users but a "nightmare" for law enforcement and forensics workers, the team at Erlangen's Friedrich-Alexander University (FAU) wrote in a blogpost about their work.

To get around this, researchers Tilo Muller, Michael Spreitzenbarth and Felix Freiling from FAU put Android phones in a freezer for an hour until the device had cooled to below -10C.

The trio discovered that quickly connecting and disconnecting the battery of a frozen phone forced the handset into a vulnerable mode. This loophole let them start it up with some custom-built software rather than its onboard Android operating system. The researchers dubbed their custom code Frost - Forensic Recovery of Scrambled Telephones.